process.env

• <Object>

返回用户的环境信息。 参阅 environ(7)。

返回的对象类似如下：

{
  TERM: 'xterm-256color',
  SHELL: '/usr/local/bin/bash',
  USER: 'maciej',
  PATH: '~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin',
  PWD: '/Users/maciej',
  EDITOR: 'vim',
  SHLVL: '1',
  HOME: '/Users/maciej',
  LOGNAME: 'maciej',
  _: '/usr/local/bin/node'
}

可以修改这个对象，但是修改的内容不会影响到进程之外。 也就是说，下面的例子是无效的：

$ node -e 'process.env.foo = "bar"' && echo $foo

下面的例子是有效的：

process.env.foo = 'bar';
console.log(process.env.foo);

为 process.env 新增属性时会将属性的值转换成字符串。 在未来的版本中，如果属性的值不是字符串、数字或布尔值，则可能抛出错误。

process.env.test = null;
console.log(process.env.test);
// => 'null'
process.env.test = undefined;
console.log(process.env.test);
// => 'undefined'

使用 delete 可以从 process.env 中删除属性。

process.env.TEST = 1;
delete process.env.TEST;
console.log(process.env.TEST);
// => undefined

在 Windows 上，环境变量不区分大小写。

process.env.TEST = 1;
console.log(process.env.test);
// => 1

Worker 线程中的 process.env 是只读的。

• <Object>

The process.env property returns an object containing the user environment. See environ(7).

An example of this object looks like:

{
  TERM: 'xterm-256color',
  SHELL: '/usr/local/bin/bash',
  USER: 'maciej',
  PATH: '~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin',
  PWD: '/Users/maciej',
  EDITOR: 'vim',
  SHLVL: '1',
  HOME: '/Users/maciej',
  LOGNAME: 'maciej',
  _: '/usr/local/bin/node'
}

It is possible to modify this object, but such modifications will not be reflected outside the Node.js process. In other words, the following example would not work:

$ node -e 'process.env.foo = "bar"' && echo $foo

While the following will:

process.env.foo = 'bar';
console.log(process.env.foo);

Assigning a property on process.env will implicitly convert the value to a string. This behavior is deprecated. Future versions of Node.js may throw an error when the value is not a string, number, or boolean.

process.env.test = null;
console.log(process.env.test);
// => 'null'
process.env.test = undefined;
console.log(process.env.test);
// => 'undefined'

Use delete to delete a property from process.env.

process.env.TEST = 1;
delete process.env.TEST;
console.log(process.env.TEST);
// => undefined

On Windows operating systems, environment variables are case-insensitive.

process.env.TEST = 1;
console.log(process.env.test);
// => 1

process.env is read-only in Worker threads.